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Genes control age of menopause

By Andrea Graves

Women wondering how long they can delay having children should look to their mothers, as new research shows the factors determining the age at which a woman’s reproductive life ends are about 85 percent inherited.

The information might help women estimate how long they will be fertile, according to Jan-Peter de Bruin at the Diakonessen Hospital, Utrecht, The Netherlands, who led the team. But knowing a mother’s menopause age provides only a rough guide, he cautions.

The team is now aiming to discover which genes control the onset of menopause. “There’s probably a lot of genes involved”, de Bruin told New Scientist. He hopes that a woman may one day be able to take a blood test that scans her genotype and reveals her expected age of menopause.

Roger Gosden, a reproductive endocrinologist at McGill University, Montreal, suspects that the effect is due to genes or gene polymorphisms that influence the size of the egg store laid down before birth.

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Waste management

“The bigger the store, the later the menopause,” he says. He adds that it is also possible that genes influence the rate at which eggs are used up. Most eggs are wasted, rather than ovulated, he notes.

Slowing down this wastage would extend the lifetime of a woman’s ovaries, and this could be the eventual outcome of de Bruin’s research. If the menopause genes do promote egg wastage, they must do so by releasing proteins that could theoretically be blocked.

“We hope that one day we can get some drugs that delay the eggs leaving the pool,” de Bruin speculates.

Sets of sisters

In the study, post-menopausal sisters -118 twins and 243 non-twins – were asked how old they were when their menstrual cycles stopped. The results showed that the age of menopause was more similar between sisters, and that genetics are mainly responsible for it.

Previous studies have also shown that menopause age is dependent on genetics, but to a lesser extent. De Bruin suspects this resulted from non-random samples of the population.

Although the study indicates that the timing of menopause is largely out of a woman’s control, there are environmental factors that influence the timing of menopause. Smoking and short menstrual cycles bring it forward, and taking the contraceptive pill and having a lot of babies can delay it, according to de Bruin.

“Menopause just comes down to depletion of the follicle store (in the ovaries),” he explains.